Explorer `filterFn` does not see `index.md` files in folder children about quartz

[bachrc]

Okay it's because when we are reaching the index file, we are not adding it to the tree :

quartz/quartz/components/ExplorerNode.tsx

Line 69 in e3cfe1f

// index case (we are the root and we just found index.md), set our data appropriately

Problem is: in the filterFn function, the content of the file is lost.

We could think that we could just put the index file attribute in the folder file, but this would introduce some regression. People following the docs already rely on the data attribute to know if a FileNode is a folder :

quartz/docs/features/explorer.md

Line 109 in e3cfe1f

> You can check if a `FileNode` is a folder or a file like this: